Martian Meteorites, Gas Giants & The Search for Alien Life | Q&A

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Thanks for joining us. This is a Q&A episode of Space Nuts where we answer

astronomy and space science questions from our audience today. David wants to

know about Mars Meteor showers. Penny is asking about fly through missions

for Saturn and Jupiter. It could be messy. Andy is asking about the

gravitational effect of Jupiter on its moons, particularly Europa, and Duncan

wants to talk about alien civilizations. We will deal with all of that and

more on this episode of Space Nuts.

This is Fred Watson's favorite segment. He's back again for more

Professor Fred Watson astronomer at large. Hello. Hello, Andrew. How are you?

I am quite well. It's been a long time like an hour, two or three minutes.

Hope nobody's guests that we record these impairs. But never mind, never mind.

If they haven't figured it out by now they probably never will. That's right.

I'm pretty sure most people know how it works. I mean they just have to look at

the shirts. We're wearing every week. That's if they do it on the YouTube

channel. Well, I don't know. I don't know if they put the video on anymore

because it could be a bit a bit of a turn off. So I don't know. Anyway,

all is well with you. I trust it is. Thank you. Yes. I already knew the answer

that we have to ask because you know this is just a bit below it. Yes, that's

exactly. Why don't we try and answer some questions?

Or if you must. Well, you do. I'm just going to push them in there.

Let's go to our first question that comes from David. David Thompson here

from Ortonley Spring in the UK. Back to Mars. There's a child of the 50s and 60s.

Really in the comics. At the time, there was always a risk of meteor showers.

I'm just wondering given that Mars atmosphere is not as dense as the Earth's.

What a smaller meteorites would be able to

hit the surface of Mars and be a real hazard to anybody who's in a house there.

Find the podcast absolutely amazing. Everybody have a great day. Bye.

Thank you, David. Thanks for those kind words. I'm glad you're enjoying the podcast.

So we're back to Mars. I didn't push him there. I didn't. Everyone knows I love Mars.

But yeah, meteor showers, it brings up an interesting point. It's got a much less

significant atmosphere than Earth. So does that mean smaller things can get through?

It does. Yeah, it does. David's absolutely right. I'm delighted. We've got a listening

in Ortonley Spring. I used to drive past there very, very frequently. It's between Durham

and Sunderland in the north of England. And I was a very, very regular user of the A1M,

which goes right past Ortonley Spring. And it's lovely to hear your voice, David, and hear

that lovely North Durham accent there. The answer is yes. So because the atmosphere,

you know, the atmospheric pressure on Mars is, I think it's 0.6% of our atmospheric pressure,

which means that meteorites coming in are going to have a lot less resistance.

We know of meteorites on Mars. Many have been identified by both curiosity and perseverance

usually by their colour, but both those rovers were equipped with laser zappers that could give

us an idea of the content. And some of those meteorites have been found to be metallic.

So meteorites on Mars are something that happens. And yes, there's probably a higher risk

of damage from an incoming meteorite on Mars than on Earth. And because the likelihood is,

but their terminal velocity, the sort of final velocity after they've passed through the atmosphere,

will be much higher than it will be on Earth, just because they're not lower pressure.

And so yes, meteorite protection might turn out to be quite an important aspect of

putting humans on Mars. We haven't had any reports of, you know, how many rovers have been on Mars

now? I can think of one, two, three, four, five, six, at least six, probably more like seven or eight.

They are, Andrew's googling it as we speak. Yeah, six, six rovers. Sojourner, spirit,

opportunity, curiosity, perseverance, and jaurong. Jaunae's mission.

The Chinese one, that's right. Yep. So I did get the right answer, six. Yeah.

Yeah, it's so, none of those as to the best of our knowledge has suffered any kind of

meteoritic impact. So at least so far, so good in terms of our understanding of the meteorite

hazard on Mars. But a good question to rose, David. And if this always gives us a chance to talk

about Mars, he did ask about the danger to housing on Mars. They probably won't build houses on

Mars like they do on Earth. And because of the radiation issues, they're probably going to have

to go underground, which would protect them from anything like that. But there will be surface

something or other there one day. So that's infrastructure. Yeah, perhaps domes that they

could be susceptible, maybe. Yeah, it looks like, I mean, what we imagine is something like white

cliffs in Western New South Wales, where people live underground. They do. And that's just to get

out of the heat. That's right, that's radiation. Yes, it is. Solar radiation, that's right.

Yeah, indeed. Yeah, sort of another question. Yeah, here it is. We are constantly monitoring for

big objects that could be threatening to Earth, things that could destroy cities or regions,

or God forbid the planet itself, as we know it. What about Mars? Do we keep an eye on anything

that might hit that? So yes, to some extent, if you, you know, if you can identify

near Earth objects and look at their orbits, you would certainly find out from the analysis very

quickly, if there was any risk of one of those hitting the planet Mars. But there's probably

many small objects in the vicinity of Mars, because it's closer to the asteroid belt than we are,

which are undetectable from the distance of Earth. You know, objects that might even be as

big as Phobos, Mars is biggest moon. We would be able to detect that from Earth quite easily,

but as if we obviously can, it was discovered in the 1800s. But, you know, if you had something

that was only a few 10 meters across, which could pose a hazard to houses on Mars, that would be

hard to detect from the distance of Earth, unless it was also a near Earth object. So it was coming

close to, closer to our telescopes. Yeah. There'd be nothing much we could do about a B-thing

hitting Mars. Anyways, there would be good experiment if we wanted to test our capabilities.

Well, that's right. If there was, you know, the bigger ones are the ones that we know more about,

because they're easier to see. If something like that was looking as though it might collide with Mars.

Yes, it might be a good time to test out the theories that were put into place with the

dark mission a few years ago. Yes, whether it actually work on something a bit bigger than that.

One can only wonder, but hopefully we don't ever have to put it to the test for ourselves,

but you just never know. There's always something going on out there. There's so much stuff

bumping into it. There's something else out there. It's only a matter of time before one of them

carines into our sector and becomes a potential threat, although we seem to be finding

them more and more now, don't we, Fred? And that's the good news buzz of this story.

Two good news sides of this story. One is that the big ones are the easiest to find,

and the other is that we've been finding these things now for the last 40 years and have a good

idea of what the Earth's environment's like. Yeah. Great to hear from you, David. Great question,

and thanks for sending it in. Our next question comes from Penny. It's a short, quick one.

I think I know where this one might go, too, in terms of an answer. As Saturn and Jupiter are

gas giants, are there any plans to fly a spacecraft through the middle of one or both of them?

Interesting question, Penny. I do recall, when you're talking about the comet or asteroid impacts,

the impact with Jupiter many, many years ago that we almost got 40 jobs. It was just quite,

not quite the right angle, but we did see the aftermath of it.

That's Schumacher-Levy. Yes. Second, the one hit Jupiter, but yeah.

I don't remember what year 94 I think it might have been.

So the issue is that the gas giant aspect of these planets is really just their outer envelope

that's gassy. And we don't really know what's underneath that. The likelihood is there will be a

solid core there. It may be rocky. Some have suggested that it will be made of metallic hydrogen,

which is hydrogen in a very unusual form. So you've got a core of something called metallic hydrogen.

So flying through is not anything that's planned because it will be impossible. But even if

these gas giants were sort of gaseous all the way through, it still would be a very hard thing

to achieve because you're entering an atmosphere, you'd have to slow the rocket, the spacecraft down,

enormously, in order to prevent it from just melting by friction with the atmosphere, which is

what happened to Cassini. Cassini was plunged into a Saturn's atmosphere at the end of its mission

in 2017. It didn't burn up because there's no oxygen in Saturn's atmosphere, but the friction

made it melt basically, it just melted and fell to pieces. In fact, NASA produced some real

tear-jerker footage of what that might have looked like, which we saw often at the end of the Cassini

mission. This thing, which had performed valiantly for the previous 13 years and done a marvellous

job at revolutionising our knowledge, not just of Saturn, and its rings and moons, but also

the way planets form and things like that, this footage of Cassini hitting the top of Saturn's

atmosphere and having its antennas ripped off and eventually just melting into becoming part of

the atoms of the atmosphere of Saturn. And then, you know, any mission to try and penetrate down

through the atmosphere would struggle because of the rapid increase in density. The fact that you've

got to slow the spacecraft down in order to stop it just burning up my friction. And I think

one of the Jupiter missions, I can't remember which one, might have been Galileo, actually sensed

as it hits Jupiter's atmosphere to burn up again or to melt. I think there were sensors on board

giving us some readings of what the conditions were like. Yeah, I think the other big problem

would be pressure, wouldn't it, if you tried to fly through. Yeah, so the pressure just goes up

probably exponentially at some level. Yeah. And Penny might be interested to know that there are some

missions slated for the near future, Europa Clipper, which will launch in, oh, it's already launched.

It should receive its 2030. There's the juice mission which launched in 2023, which arrived in

2031 and Dragonfly with the helicopter off to Titan. Yeah, we'll launch in 2028. So they're

more interested in some of the moons around those gas giants, but yes, they're fascinating. And

of course, we're most interested in Europa Clipper because we want to know if anything's living in

the ocean. And maybe there is. Maybe there isn't. Who knows? It could just be made of jelly. We don't

really know. Although the juice mission is more likely to figure all that out. Boom, boom. Thank

you, Penny. Lovely to hear from you. This is Space Nuts Q&A edition with Andrew Dunkley and

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four systems that came with us. Space Nuts. And speaking of Europa and Jupiter,

we've got a question now from Andy. This is Andy, the train driver from London.

Just got a question about Europa. I know Europa erupts because it's being

sort of squeezed by the gravity of Jupiter. But what I don't understand is if Europa is being

affected by Jupiter's gravity, why is it not just being pulled closer to Jupiter? I thought gravity

pulls things down like when you throw a ball in the air, gravity pulls it back down. I don't

understand how Europa is being squeezed. That suggests to me that it's being affected by gravity

from all directions. It's not squeezed it like a lucky could squeeze a tennis ball.

Maybe you can shed some light on this or tell me that I'm blocking up the wrong tree.

Anyway, thanks for the podcast. Guys, really interesting and see you on the next one.

It's Jordy's job to back up the wrong tree, but that's actually done, Andrew, I like to say.

Your point is well taken, Andy. It's not just Europa though. There are several moons

orbiting the gas giants that do get that squeeze effect. Titan, I think, is one of them.

I'll look probably all of them to some degree, but Europa, yeah, it's in a difficult position.

It's a good question. No, why don't they just get sucked in?

Absolutely. It doesn't, but we're not gas giant.

No, the same thing happens to our moon though. It's actually probably, I think the moon that

Andy's thinking of is EO, which is the innermost of the moon, the big moon, big four moons of Jupiter.

And it is the one that gets the most squeezing and squashing because of its proximity to Jupiter.

Europa probably also has the same phenomenon, and there may be eruptions of it

on Europa that are possibly a bit like Enceladus where you've got stuff streaming out

through the cracks in the ice. But the genuine volcanic eruptions, which they really are,

it's hot lava, is what take place on EO, the innermost of those moons.

So the way to understand this is to realise that if you've got an object in a very strong

gravitational field, first of all, let me just clarify. The reason why objects in Europa

around other objects don't just get pulled in. They are getting pulled in, but they've got a

forward motion that compensates for the pull. So basically the motion of the object through space

is what balances out the gravity of a giant like Jupiter. And so the greater the gravity of a

planet, the faster it satellites have to orbit in order not to fall in. And so that's

that's the mechanism that stops these things just immediately being sucked in to Jupiter there,

already moving. And that comes about, why are they moving? Because they were formed that way,

with the way the planets and their satellites evolve, the way they formed, they're basically

swirling around right from the start, and that swirling motion is what stops, which is fossilised

in the planets themselves and the moons of the planets, and stops them falling into their

parent object. But the squeezing and squashing comes from what we call the tidal effects,

and it is actually exactly the same thing that gives rise to tides on the earth.

But let's concentrate from in it on EO, here's this little world, right next to

gas giant Jupiter. One side of EO is feeling the gravitational pull of Jupiter. The other side is

as well, but it's feeling slightly less because it's further away, because the gravitational pull

falls off as as the distance squared, one over the distance squared. So further on the further

side of EO from Jupiter, it's going to feel less force. And that is what contributes to this

tension that there is, and basically elongates the planet slightly in the direction of Jupiter. Now

why we talk about squashing and squeezing is that throughout the orbit of EO, she's not a planet,

it's a satellite, but around the orbit of EO as it goes around, is not circular. So sometimes

that force is greater than others, that tension that's trying to pull it apart is greater than

at other times, and basically it's that squashing, stretching really is the best word for it, as it

goes around, as it goes around Jupiter, that change in the stretch force that's being applied

is what generates the heat that causes these eruptions to continually take place.

That's called the tidal effect, the fact that one side of a body feels a different gravitational

force from the other. It's what makes us susceptible if we fall into a black hole to

spaghettification. Spaghettification is just a nicer word than tidal effects.

So you've got a real combination of a factor. That's right. You've got the gravitational effect,

you've got all the little dynamics, or sort of coinciding to keep these things from falling into

the planet, but there's a tug of war going on. I saw a really good demonstration online,

probably three or four weeks ago on how the tides work on earth. And of course most people,

and I must confess, guilt here, assume that the moon causes the water to rise and then fall,

but it's not. It's the fact that the earth is rotating, the moon is orbiting, and there's always

a wave. It's just always there. And it's just that when the moon reaches your vicinity,

that lump of water comes up. And it goes down again. It's not the water so much rising. It's

always risen in proximity to the moon. Am I right? You are. You're partly right. Because it's a

bit more time. You're going to miss something. Yeah. And that doesn't explain the bulge on the other

side, because as you go, you get a high tide every 12 hours, not every 12 hours. And that's because

again, it's the tidal effect. So the moon's pulling on the ocean on the near side.

It's also pulling on the earth itself. And that leaves behind the water on the other side. So you

get a bulge on each side. That's iron works. Fascinating. It's worth looking up that demo. I didn't

read your fine print, obviously, but yeah, that makes sense. So the water's being pulled

or dragging with it. And then the water's being left behind on the other side. So you've got two

bulges, two bulges. Exactly. So it's fascinating. And that's going to be what's happening to all these

moons in various ways. If I have no water, something else is being... Well, that's right. It's the

rock. The rock does it as well. The sand is true on earth. The rock goes up and down as well.

I've got a question for Andy, though. If he's ever getting back to us, I'd like to know what

sort of trains he drives. Yeah, because, yeah, I'm a bit of a train myself. Train drivers are my

heroes. I live next door to a retired train driver. So when we flew into Dubbo the other day,

I looked down at the rail maintenance facility. It's a brand new facility that's just been built

in Dubbo. And they're fitting out all the new regional trains. And you can see them all lined up,

bright red, all getting ready to go. They're putting all the furniture in them and the Wi-Fi systems

and yeah, they'll be rolled out pretty soon. Not exactly sure when, but the plan is soon. That's

the answer to the question officially. Have you ridden on new metro trains here in Sydney?

Yes, I have. Yes. So you'll know that they drive 100 kilometers now with no driver. You can

stand at the front, look out the front window and pretend you're driving it. Yeah. I've done that

in a taxi in San Francisco. Oh, yes, you have drivers for Ivalous taxi. That's next level.

That's just amazing, but yeah, pretty incredible stuff. Thanks, Andy. I really enjoyed that question.

And yeah, if you want to tell us what sort of train you drive, send us another message we'd love

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Our final question today, Fred, comes from Duncan. He said,

I've heard that a group of astrophysicists have calculated that there are an estimated 1,000

alien civilizations spread across the Milky Way. But the Milky Way is 100,000 light years across.

How far away would an advanced civilization have to be, in practical terms, to be uncontactable?

In other words, are we realistically given the distances involved effectively alone?

Yes, is the answer? Yeah. And it's not just about the distance. It's also about the time.

Because 1,000 civilizations, whether in a galaxy that's 12 billion years old,

they might, well, have turned up and gone long ago or still be in the future.

And because I assume that we all coexist.

That's right. And we probably don't. There's actually a really nice piece.

No, let me see if I can find it to direct Duncan to it. It's on one of the science media

came today. So actually, I think is, oh, where is it? Sorry, I've lost it.

Yeah. It's basically a summary of thinking by the likes of Richard Feynman and other great

minds. And the bottom line is, you say exactly what I've been saying, it's not just the distances.

It's the time that the era in which you live. And it's very unlikely that we'd find

communicable civilizations within the same time zone that we're living in, if I can put it that

way. It's actually on, it is on again, on the brighter side of news. And the headline is a really

very, very thoughtful article, well worth a read, interstellar travel is impossible.

An aliens haven't visited the earth, physicists say. And it's because the laws of physics basically

make any kind of travel or even communication extremely difficult. The laws of physics are very

rigid worth having a look at. Yeah, indeed. Although there's this new book that I know that's

being written that kind of is counter to all that, but you can do that in science fiction.

Quite so. Yeah, that's why it's called science fiction. Yes, that's what it is.

By way of example, though, if I may, Duncan, if you were to be aware of an advanced

communicative civilization on a rocky planet orbiting Alpha Centaurier, for example,

and you sent them a message, it would take, just try to remember, 4.37 years to get there.

And that means a return message if they answered you immediately, would mean that you would not

get a reply for 8.74 years. Yep, give or take. But let's round that out. They were

decade because you know what the bureaucracies like around Alpha Centaurier, they're not going to,

you know, they're going to take a couple of years to figure out what they want to say.

But that's the reality of it, isn't it? And that's our nearest potential

yeah, neighbor. It's true. And I mean, the point that this article makes is,

you know, we live in a bubble of radio radiation, which are all the transmissions from Earth

that's now basically 100 light years in radius because we've been sending radio transmissions

for about 100 years. And all right, what's that 100 divided by? It's 1,000th of the

damage of the galaxy. And so, you know, it's hardly any distance at all. So yeah, it's,

it's on, in a way, an uncomfortable reality, to all the intents and purposes we're alone, we're

uncontactable, we are alone. That is good side because we're unlikely to be picked on by

any voracious aliens. But yeah, yeah, I think we've got to be realistic about it,

even if there are 1,000 alien civilizations with advanced technology in our galaxy,

we are probably never going to be in a position to communicate with them, or and certainly not

be able to travel to them in any meaningful way. And so, even if we're not alone, we are alone.

Yes, that's right. Exactly. You know, of that 1,000 civilizations, maybe 500 of them have been

and gone, and 500 of them are yet to evolve. Do you concur with that estimation? Or you don't

think it's... I have seen similar figures being quoted. Not that there's that number of

civilizations, but there might be that sort of number of habitable planets that might be Earth-like.

We don't know whether being Earth-like necessarily means you evolve an intelligent species.

Of course, it's done at once, but yeah, the only time could be, because the circumstances have

to be perfectly right, although we're assuming humanoid-type carbon-based life forms, but there

could be others out there that were created a completely different way. That's the stuff of

imagination at the moment, but it's a possibility, I suppose. And of course, we'll look like

Dill's next week when a massive alien mothership sets itself down on top of the White House, and

yeah, to rescue us all. Maybe. Maybe. Gosh, thanks, Duncan. Thanks to everybody who's

setting questions. Please send them into us. I do have a bit of homework sort of. We've got a

question twice now. I've received it from Mike in New York. Mike, you've sent us a question in

about black holes, an audio question. The whole guts of the question got cut off somehow,

and so we got the first, we got your preamble, then you started asking the question, then there

was about five hours of nothing, probably about four, you know, 20 seconds. And then we heard

you say goodbye, so we don't actually have the question. So if you'd like to send it again,

please do. I don't know what happened there, but yeah, it's the internet, so that's what happened

there. But yeah, Mike would love to get that question, so we can run with it. And any questions you

want to send in via the Ask Me Anything tab at the top of our website, space and ads podcast.com,

space and ads.io. And don't forget to tell us who you are and where you're from. Thank you Fred,

as always, it's been a lot of fun. Absolutely. It's great questions. Good to hear everybody's voice

and nice to see their questions. Thank you. Indeed. That's Professor Fred Watson, astronomer at

large. And thanks to here in the studio, couldn't be with us today. He got stopped by border security,

and they realised he was an alien. It comes from New Zealand, it made sense. So he's been arrested.

He might be back next week. And from me, Andrew Dunkley, thanks for your company,

we'll catch you on the next episode of Space Nuts. Bye-bye.

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